$ 
a) al eee Recent Literature. 467 
most fundamental importance in producing the variations upon 
ut no one can read them without profit. 
nize that Professor Cope has attempted to answer a question 
lying below the law of natural selection. He has attempted to 
show why variations appear when they are needed and how it is 
that many animals may vary simultaneously in the same direc- 
tion. It is hardly time to pass judgment upon his views, but it 
certainly seems that the observations and suggestions embodied 
in this book remove many of the difficulties which have been 
found in the way of the descent theory when viewed from the 
stand-point of pure Darwinism. 
by Professor Cope heterology. Plate XVI. represents five types 
of the new world Iguanidz, and Plate XVII. as many of the 
old world Agamide —H.. W. Conn. 
species; they belong to the genera Pinus, Abies, Fagus, Liquid- 
ambar, Rhizomites, and Potamogeton. Several plants, referred 
to the Oligocene by Ludwig, are Pliocene. 
* Die Oberpliocaen Flora aus den Baugruben des Klaerbeckens bei Niederrad 
und der Schleuse bei Hoechst a. M. 47 pages, 4to, 4 plates. By Th. Geyler u. 
F. Kinkelin. Abhandl, d. Senckenberg. Naturforsch. Gesellsch., 1887. 
